1. Field of the Invention
The present invention relates to exhaust gas filters, and more particularly to particulate matter collection and catalytic conversion structures useful in trapping the particulates and fumes of combustion emitted by a diesel power plant.
2. Description of the Prior Art
Diesel engines are characteristically very effective producers of power, primarily because of the high pressures and temperatures of combustion process thereof. While under ideal conditions the power efficiency of the diesel cycle is an attractive feature, in practice the process is infested with numerous faults. For example, once some wear has occurred and the ideal design conditions of combustion are no longer in place, the process becomes quite dirty with large by-products of incomplete combustion and particulates emitted. Those traveling the nation's highways will therefore be familiar with the dark exhaust plumes typically produced by a diesel powered truck. In fact it is the presence of these dark plumes that distinguishes the power plant.
In the recent past the foregoing pollution producing attributes of diesel power have had some attention in the rulemaking process of the US Environmenal Protection Agency [EPA] and heavy vehicles on our highways will therefore be regulated in their exhaust output by the year 2004. This regulatory impetus, along with the earlier concerns over the diesel exhaust, have focused public attention and techniques for trapping and collecting diesel exhaust products are now extensively sought. Exemplary teachings of such mechanisms can be found in U.S. Pat. Nos. 4,183,896 to Gordon; 3,946,748 to Frankfurt; and 4,852,349 to Abthoff et al. While suitable for the purposes intended each of the foregoing teachings either solves the pollution problem by mechanical traps or filters, or by chemical or catalytic processes. The synergistic benefits of a combination of both techniques have had little attention.
Catalytic processes typically rely on expensive material structures, such as platinum, and for that reason the catalyst is a significant cost component of any exhaust treating device. As a consequence techniques that either prolong the useful life of the catalyst, or allow for its convenient cleaning, are an economic necessity in any drive for cleaner exhaust. One factor inherent in the life of the catalyst is the accumulation of soot and condensate on the catalyst surfaces, a problem that is particularly exacerbated in a diesel process. Techniques that trap, reduce and allow for convenient cleaning of this accumulate are therefore desired and it is one such technique that is disclosed herein.